Lubricating oil thickened to a grease consistency with a bishydantoin



temperatures. made in recent years in producing improved aircraft United States Patent 3,047,498 LUBRICATING 01L THECKENED TO A GREASE CONSlfiTENCY WKTH A EHSHYDANTOIN Joseph J. McGrath, Monroeville, and .lohn'P. Pellegrini,

Jr.,-Pittsburgh, Pa, assignors to Gulf Research & Development Company, Pittsburgh, Pa, a corporation of Delaware No Drawing. Filed Sept. 26, 1960, Ser. No. 58,221 11 Claims. (Cl. 25228) This invention relates to improved lubricating compositions and more particularly to lubricants suitable for high temperature lubrication comprising a lubricating oil thickened primarily with certain high melting bishydantoin compounds.

Y The trend in design of modern aircraft has accentuated the need for greases which will lubricate antifriction bearings operating at high rotational speeds and high While considerable progress has been greases some difficulty has been encountered in producing a grease which will effectively lubricate bearings operating at high rotational speeds and high temperatures for prolonged periods of time. Conventional aircraft greases currently available have failed to meet the stringent requirements on such a lubricant.

We have discovered that a lubricating composition having improved lubricating characteristics for an extended period of time when used to lubricate bearings operating at an elevated temperature under high rotational speeds can be obtained by incorporating into a lubricating oil in oil thickening proportions of a bishydantoin having the following structural formula:

wherein R is selected from the group consisting of alkyl, aryl, alkaryl, aralkyl and cycloalkyl radicals and R R and R are selected from the group consisting of hydrogen, alkyl, aryl, alkaryl, aralkyl and cycloalkyl radicals. Thus, the improved lubricating composition of our invention comprises a dispersion in a lubricating oil of a sulficient amount to thicken the lubricating oil to a grease consistency of a bishydantoin compound of the type designated above. In some instances a secondary oil thickening agent comprising an organophilic siliceous material is also employed.

The radicals designated as R in the formula given hereinabove are like radicals. Also, the radicals designated as R are like radicals. Except for the limitation that R can not be hydrogen, the radicals designated as R and R can otherwise be the same or different radicals. A preferred group of compounds are those wherein R and R are the same radicals, especially lower alkyl radicals containing from 1 to 8 carbon atoms. The radicals designated as R and R can be the same or different radicals, either one or both of which can be the same or diiferent from the substituents designated as R and R A preferred group of compounds are those wherein R and R are the same radicals, especially hydrogen. The alkyl substituents preferably contain from 1 to 8 carbon atoms, i.e., methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl and octyl radicals. The alkaryl and aralkyl substituents are preferably those wherein the alkyl portion of the substituent contains not more than 2 carbon atoms, i.e., tolyl, ethylphenyl, benzyl and phenylethyl radicals. More than 8 carbon atoms in the alkyl radical and more than 2 carbon atoms in the alkyl portion of the alkaryl and aralkyl radicals are less desirable inasmuch as the thermal stability of the hydantoins is adversely affected when the lubricant produced therefrom is subjected to a high temperature and high rotational speeds over extended periods of time. The aryl radical can be mono or bicyclic, i.e., phenyl and naphthyl radicals. The cycloalkyl radicals are preferably the cycl opentyl and cyclohexyl radicals.

The amount of the oil thickening agent which we use Whether simply the bishydantoin compound or a mixture of the bishydantoin compound and an organophilic siliceous material is an amount sufiicient to thicken the lubricating oil to a grease having the desired consistency. In general, this amount comprises about 10 to about 60 percent by weight of the total composition. When a mixture of the bishydantoin compound and an organophilic siliceous material is used, the weight ratio of the bishydantoin compound to the organ-ophilic siliceous material will vary depending upon the characteristics desired in the ultimate composition. In general, however, the ratio of the bishydantoin compound to the organophilic siliceous material is between about 1:1 and about 20:1.

The bishydantoins can be prepared by any known chemical procedure. Neither the compounds per se nor their method of preparation constitutes any portion of the invention. For example, the bishydantoin can be prepared by condensing two moles of a hydantoin with one mole of an aldehyde or a ketone. One method for preparing a 1,l'-methylenebis(alkyl-hydantoin) is disclosed in U.S. Patent No. 2,417,999 which issued on May 25, 1947 to J. F. Walker. According to the patent, one mole of an alkyl substituted hydantoin is reacted with two moles of formaldehyde in an aqueous medium comprising concentrated hydrochloric acid. A salt of Zinc or cadmium serves to catalyze the reaction. An excess of formaldehyde is undesirable since it favors resin formation; The reaction mass comprises about 15 to 35 percent water at the start of the reaction, hydrogen chloride being present therein to the extent of at least one part of hydrogen chloride to four parts of water. The reaction is carried out at 30 to C. in the presence of 0.5 to 50 percent by weight of a catalyst such as zinc chloride or cadmium chloride. Upon completion of the reaction,

the reaction product is washed with water and then puri tied. Purification is accomplished by dissolving the product in caustic solution, filtering, neutralizing with hydrochloric acid, washing with warm water and then drying. Similar procedures can be used in preparing other bishydantoins.

Specific examples of some of the bishydantoins having a structural formula as designated hereinabove are:

1, l -methylenebis 5-n-propylhydantoin) 1, l -methylenebis S-isooctylhydantoin) l, 1 '-methylenebis S-methyl-5-ethylhydantoin) 1,1-methylenebis(S-methyl-S-isobutylhydantoin) 1 1 '-methylenebis 5 ,5 -dimethvlhydantoin) 1,1 1,1 1,1 1,1 1,1 1,1 1,1 1,1 1,1 -methylenebis(5,S-dicyclopentylhydantoin) spa-race 1, 1 -methyle nebis 5,5 -dicyclohexylhydantoin) 1,1-dimethylmethylenebis ,5 -dimethylhydantoin) 1 1 '-diisobutylmethylenebis 5 ,idimethylhydantoin) 1, 1 -diisooctylmethylenebis 5 ,5 -dimethylhydantoin) 1, 1-diphenylmethylenebis(5,5-diphenylhydantoin) 1,1-bis 5 ,5-dimethyl-2,4-diketoimidazolidyl-l ethane 2,2-bis 5 ,5 -dimethyl-2,4-diketoimidazolidyl-l )prcpane 3 ,3-bis 5 ,5 -dimethyl-2,4-diketoimidazolidyl-1 )hexane 4,4-bis 5 ,5 -dimethyl-2,4-diketoimidazoiidyl-l )octane 4,4 bis(5,5 dimethyl 2,4 diketoimidazolidyl-l)2,6-

dimethyloetane 5,5 bis(5,5 dimethyl 2,4 diketoimidazolidyl-1)9- methyldodecane 1,1 bis(5,S-dimethyl-2,4-diketoimidazolidyl-l)l-phenylmethane 1,1 bis(5,5 dimethyl 2,4 diketoimidazolidyl-1)ibenzylethane 1,1 bis(5,5 dimethyl 2,4 diketoimidazolidyl-l)1- (p-tolyl)propane 2,2 bis(5,5 diphenyl 2,4 diketoimidazolidyl-1)4- phenylbutane The organophilic siliceous materials which we can employ as secondary thickening agents in the lubricating composition of this invention are exemplified by bentonite-organic base compounds known commercially as Bentones and finely divided organo-siliceous solids such as the esterified siliceous solids known commercially as Estersils. The amount of the organophilic siliceous material employed may vary over wide limits depending upon the particular compound employed, the particular oil with which the siliceous compound is blended and the properties desired in the ultimate composition. While the organophilic siliceous material, when used, may comprise as much as percent by weight of the total composition, We prefer to use smaller amounts, that is, in order of about 1 to about 10 percent by weight. It should be understood, however, that depending upon the consistency of the composition desired and upon the bishydantoin compound content of the composition less than 1 percent or more than 10 percent of the organophilic siliceous material can be employed.

Typical bentonite-organic base compounds which can be employed in accordance with the invention are compounds composed of a montmorillonite mineral in which at least a part of the cation content of the mineral has been replaced by an organic base. Clays that swell at least to some extent on being contacted with water and contain as a primary constituent a mineral of the group known as montmorillonites are generally referred to as bentonites. Such clays, which contain exchangeable alkali metal atoms either naturally or after treatment, constitute the raw materials employed in making the bentonite-organic base compounds used in the compositions of this invention. So far as known, all naturally occurring montmorillonites contain some magnesium and certain of them, as exemplified by Hector clay, contain such a high percentage of magnesium that they largely have magnesium in place of the aluminum content characteristic of the more typical montmorillonites.

The bentonite-organic base compounds are preferably prepared as described in U.S. Patent No. 2,033,856, issued March 10, 193 6, by bringing together the bentonite and the organic base in the presence of aqueous mineral acid to effect base exchange. The organic bases should preferably be titratable with mineral acids. Among these reactive bases are many alkaloids, and cyclic, aliphatic, and heterocyclic amines. The bentonite-organic base compounds used in preparing the lubricating compositions of this invention are preferably those prepared by bringing together a bentonite clay and such organic bases as aliphatic amines, their salts, and quaternary ammonium salts. Examples of such amines and salts are: decylamine, dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, hexadecyl ammonium acetate, octadecyl ammonium acetate, dimethyldioctyl ammonium 4 acetate, dimethyldidodecyl ammonium acetate, dimethyldodecylhexadecyl ammonium acetate, dimethyldicetyl ammonium acetate, dimethylhexadecyloctadecyl ammonium acetate, dimethyldioctadecyl ammonium acetate, and the corresponding chlorides and quaternary ammonium chlorides. The organic bases employed should be such as to impart substantial organophilic properties to the resulting compounds. The preferred bentonite compounds are prepared from quaternary ammonium compounds in which the N-substituents are aliphatic groups containing at least one alkyl group with a total of at least 10 to 12 carbon atoms. When aliphatic amines are used they preferably contain at least one alkyl group containing at least 10 to 12 carbon atoms.

While the long chain aliphatic amine bentonite compounds are readily dispersible in practically all oil bases, dispersion of the short or single chain aliphatic amine bentonite compounds, in the oil, particularly mineral oils and synthetieoils other than ester lubricants, can be facilitated by the use of one or more solvating agents. Suitable solvating agents are polar organic compounds such as organic acids, esters, alcohols, ethers, ketones, and aldehydes, especially low molecular weight compounds of these classes. Examples of suitable solvating agents are: ethyl acetate, acetic acid, acetone, methyl alcohol, ethyl alcohol, benzoyl chloride, butyl stearate, cocoanut oil, cyclohexanone, ethylene dichloride, ethyl ether, furfural, isoamyl acetate, methyl ethyl ketone, and nitrobenzene. In cases where the use of a solvating agent is desirable for effecting more rapid and more comcomplete dispersion of the organic bentonite compound in the oil, ordinarily only a relatively small amount of such agent may be necessary. However, as much as about 50 percent by weight based on the amount of the bentonite compound can be used.

Typical estersils which can be employed in accordance with the invention are described in US. Patent No. 2,657,149, issued October 27, 1953 to R. K. Her. The estersils are organophilic solids made by chemically reacting primary or secondary alcohols with certain siliceous solids. In brief, the estersils are powders or pulverulent materials the internal structure or substrate of which have an average specific surface area of from 1 to 900 square meters per gram. The substrate has a surface of silica which is coated with --OR groups, the coating of -OR' groups being chemically bound to the silica. R is a hydrocarbon radical of a primary or secondary alcohol containing from 2 to 18 carbon atoms. The carbon atom attached to the oxygen is also attached to hydrogen.

The estersil substrates are solid inorganic siliceous materials which contain substantially no chemically bound organic groups prior to esterification. The substrates are in a supercolloidal state of subdivision, indicating that whatever discrete particles are present are larger than colloidal size. In general, the supercolloidal substrates have at least one dimension of at least 150 millimicrons. The supercolloidal particles may be aggregates of ultimate units Which are colloidal in size.

When we employ an estersil it is advantageously one in which the ultimate units have an average diameter of 8 to 10 millimicrons. The substrates advantageously have specific surface areas of at least 25 square meters per gram and preferably at least 200 square meters per gram.

The estersils made from most alcohols become organophilic when they contain more than about ester groups per square millimicrons of surface of internal structure. They become more organophilic as the ester groups increase. Thus, the products which contain 100 ester groups per 100 square millimicrons of substrate surface are more organophilic than those that contain only 80 ester groups. When the estersils contain at least 200 ester groups per 100 square millimicrons of substrate surface, the estersils not only are organophilic but also are hydrophobic. Thus, the more highly esterified prodnets are particularly desirable where the lubricant made therefrom comes in contact with water. When C to C alcohols are used in preparing the estersils, the estersils may contain from 300 to 4-00 ester groups per 100 square millimicrons of substrate surface. Thus, a preferred group of estersils are those prepared from the C to C alcohols. The estersils, as noted above, are powders or pulverulent materials. The estersil powders are exceedingly fine, lightand fiufiy. The bulk density of preferred estersils is in the order of 0.15 to 0.20 gram per cubic centimeter at 3 pounds per square inch and in the order of about 0.30 gram per cubic centimeter at 78 pounds per square inch. The estersils are available commercially and thus the estersils per se and their preparation constitute no part of this invention.

The lubricating oil in which the bishydantoin compound and the secondary thickening agent, when used, are

incorporated is preferably a lubricant of the type best suited for the particular use for which the ultimate composition is designed. Since many of the properties possessed by the lubricating oil are imparted to the ultimate lubricating composition, we advantageously employ an oil which is thermally stable at the contemplated lubricating temperature. Some mineral oils, especially hydrotreated mineral oils, are suiiiciently stable to provide a lubricating base for preparing lubricants to be used under moderately elevated temperatures. Where temperatures on the order of 400 F. and above are to be encountered, synthetic oils form a preferred class of lubricating bases because of their high thermal stability. The synthetic oil can be an organic ester which has a majority of the properties of a hydrocarbon oil of lubricating grade such as di-2-ethylhexyl sebacate, dioctyl phthalate and dioctyl azelate. Instead of an organic ester, we can use polymerized olefins, copolymers of alkylene glycols and alkylene oxides, polyorgano siloxanes, polyaryl ethers and the like.

The liquid polyorgano siloxanes and certain polyaryl ethers because of their exceedingly high thermal stability form a preferred group of synthetic oils to which the bishydantoin compound and organophi lic siliceous materials are added. The polyorgano siloxanes are known commercially as silicones and are made up of silicon and oxygen atoms wherein the silicon atoms may be substituted with alkyl, aryl, alkaryl, aralkyl and cycloalkyl radicals. Exemplary of such compounds are the dimethyl silicone polymers, diethyl silicone polymers, ethylphenyl silicone, polymers and methyl-phenyl silicone polymers. Exemplary of an exceedingly good polyaryl ether is a poly-plienyl ether, i.e., m-bis(m-phenoxyphenoxy)benzene.

If desired, a blend of oils of suitable viscosity may be employed as the lubricating oil base instead of a single .oil by means of which any desired viscosity may be secured. Therefore, depending upon the particular use for which the ultimate composition is designed, the lubricating I oil base may be a mineral oil, a synthetic oil, or a mixture of mineral and/or synthetic oils. The lubricating oil content of the compositions prepared according to this invention comprises about 40 to about 90 percent by weight of the total composition.

In compounding the compositions of the present invention, various mixing and blending procedures may be used. In a preferred embodiment of the invention, the lubricating oil, the bishydantoincompound and the secondary thickener, if used, together with a solvating agent and conventional lubricant additives, if desired, are mixed together at room temperature for a period of 10 to minutes to form a slurry. During this initial mixing period some thickening is evidenced. Some lumps may be formed. The slurry thus formed is then subjected to a conventional milling operation in a ball mill, a colloid mill, homogenizer or similar device used in compounding greases to give the desired degree of dispersion. In the illustrative compositions of this invention, the slurry was passed twice, by means of a pump, through a Premier the mill.

The lubricating composition of this invention can contain conventional lubricant additives, if desired, to improve other specific properties of the lubricant without departing from the scope of the invention. Thus, the lubricating composition can contain a filler, a corrosion and rust inhibitor, an extreme pressure agent, an antioxidant, a metal deactivator, a dye, and the like. Whether or not such'additives are employed and the amounts thereof depend to a large extent upon the severity of the conditions to which the composition is subjected and upon the stability of the lubricating oil base in the first instance. Since the polyorganosi'loxanes, for example, are in general more stable than mineral oils, they require the addition of very little, if any, oxidation inhibitor. When such conventional additives are used they are generally added in amounts between about 0.01 and 5 percent by weight based on the weight of the total composition.

In order to illustrate the lubricating characteristics at an elevated temperature and high rotational speeds, grease compositions of the invention were subjected we test procedure similar to that outlined by the Coordinating Research Council Tentative Draft (July, 1954), Research Technique for the Determination of Performance Characteristics of Lubricating Grease in Antifriction Bearings at Elevated Temperatures, CRC Designation L-35. According to the procedure used to evaluate the compositions, 3 grams of the grease to be tested are placed in a bearing assembly containing an eight-ball SAE No. 204 ball bearing. In general, bearings fabricated from high speed tool steel and ball retainers fabricated from silverplated beryllium-copper (MRC204S17) are used as both test and outboard bearings. The bearing assembly which is mounted on a horizontal spindle is subjected to a radial load of 5 pounds. The portion of the spindle upon which the test bearing assembly is located is encased in a thermostatically controlled oven. By this means the temperature of the bearing can be maintained at a desired elevated temperature which in the tests reported hereinafter was 400 F. The spindle is driven by a constant belt-tension motor drive assembly, capable of giving spindle speeds of 20,000 revolutions per minute. The

spindle is operated on a cycling schedule consisting of a series of periods, each period consisting of 20 hours running time and 4 hours shutdown time. The test continues until the lubricant fails. The lubricant is considered to have failed when any one of the following conditions occurs, (1) spindle input power increases to a value approximately 300 percent above the steady state condition at the test temperature; (2) an increase in temperature at the test bearing of 20 F over the test temperature during any portion of a cycle; or (3) the test bearing locks or the drive belt slips at the start or during the test cycle.

The oils used in preparing the lubricating compositions summarized in Table I were synthetic oils. The m-bis-(mphenoxyphenoxy)benzene is marketed by Monsanto Chemical Company. DC 550 Fluid is marketed by Dow- Corning Corporation and is a methylphenylsiloxane polymer having as typical characteristics a viscosity at oneness 7 Table I face area comprises about 285 to 335 square meters per gram. The product has a pH in a 50-50 methanol-Water mixture of 8.0 to 9.0 and a bulk density of 19 to 20 Composition, Percent By Weight A B C D pounds bi f ot;

While our invention has been described with reference Lu e gsfi 6 72 60 to various specific examples and embodiments, it will be gg gi gggfigggf gfijgf i understood that the invention is not limited to suchex- P Za 63 amples and embodiments and may be variously practiced 2238i;ga,5-r%ieifi;1%mn% 33 25 40 33 Within the scope of the claims hereinafter made. Secondary ic 'enerime y W 9 i A 10 Iniia c t ib iii bentomte 4 3 4 l. A lubricating composition comprising a dispersion e (ASTM 13217- in a lubricating oil of a sufiicient amount to thicken the 5 oigvorked 249 317 312 215 lubricating oil to a grease consistency of a bishydantoin ggg gg g w 305 347 380 242 having the following structural formula:

13500-52) f 450+ 450+ 450+ 450+ R Performance Life, Hrs.Pope

Spindles, 20,000 rpm. at 400 F". a 552+ a 502+ 11 527+ n 500+ R B Test discontinued-mo failure occurred. R1 (f 0:0 R (ID-R The long performance life of the compositions of the HNC=O inventionlglt afighfmtafignalbspgeddand a hlgh t wherein R is selected from the group consisting of alkyl, mm is $6 em Tom t a We aryl, alkaryl, aralkyl and cycloalkyl radicals and R R Other lubricating compositions Within the scope of the and R3 are selected from the group consisting f h 18n1v7e1n7t1on are1 lihstgat'g 1H 51 2 0 gg iz drogeri, alkyl, aryl, alkaryl, aralkyl and cycloalkyl 1s marce e y enera ec ric om y a radica S, a water-whlte t0 amber llquld P y 0f the general 5 2. The lubricating composition of claim 1 wherein the formula lubricating oil is a polyorgano siloxane.

s OSi(cH3)2 OSi(CH3)2 3. A lubricating composition comprising'a dispersion o a in a lubrlcatmg 011 of a sufiicient amount to thicken the It1 has a viscosliy at F. of 3387 CentlStOlffS, at 0 1 3O lubricating oil to a grease consistency of a mixture of a f i' t i at {g t 58 2; 5 i bishydantoin having the following structural formula: .o cenisoesan a .o ,cenisoes.

Estersil GT is marketed by E. I. du Pont de Nemours and Company and consists of an amorphous silica coated R N-- -N R with approximately 340 butoxy groups per 100 square Z R1 millimicrons of surface. The product is a white granu- 1 7 lar solid comprising 88 to 89 percent SiO having an O:OM1 HN C=O ultimate particle size of 8 to 10 millimicrons. The surwherein R is selected from the group consisting of alkyl,

Table II Composition, percent By Weight E F G H I ll K L M N O P Q R B T Lubricating Oil:

DC 550 Fluid 04 50 G.E. Silicone 81717.

Di-2-ethylhexyl sebacate m-Bis (m-phenoxyphenoxy) benzene... Primary Thickeuer:

1,1t- Methylenebis (5,5-diethylhydan- 1,1t- Methylenebis (5, 5-diisooctylhydau- 1,1t- I\ Iethylenebis (5,5-dibenzylhydan- Secondary Thickener:

Dimethyldicetylammonium bentonite. Dimethyldidodecylamiuonium bentou- P Dimethyldioctylamrnonium hentonita Dimethyldioctadexylammonium bentonite Estersil GT. Ratio of bishydantoin compound to secondary thickener 5. The lubricating composition of claim 3 wherein the organophilic siliceous oil thickening agent is a bentoniteorganic base compound.

6. The lubricating composition of claim 3 wherein the organophilic siliceous oil thickening agent is an organophilic estersil comprising a supercolloidal substrate coated with --OR' groups, the substrate having a surface of silica and having a specific surface area of from 1 to 900 square meters per gram, the coating of -OR' groups being chemically bound to said silica and R being a hydrocarbon radical of from 2 to 18 carbon atoms,

wherein the carbon attached to oxygen is also attached to hydrogen.

7. A lubricating composition comprising a dispersion in a liquid polyorgano siloxane of a sutlicient amount to thicken the polyorgano siloxane to a grease consistency of a mixture of a bishydantoin having the following structural formula:

10 bishydantoin is 1,1'-methy1enebis(5,5-dimethylhydantoin) and the bentonite-organic base compound is dimethyldicetylammonium bentonit e.

9. A lubricating composition comprising a dispersion in a liquid polyorgano siloxane of a sufficient amount to thicken the polyorgano siloxane to a grease consistency of a mixture of a bishydantoin having the following structural formula:

wherein R is selected from the group consisting of alkyl, aryl, alkaryl, aralkyl and cycloalkyl radicals and R R and R are selected from the group consisting of hydrogen, alkyl, aryl, alkaryl, aralkyl and cycloalkyl radicals and an organophilic estersil, the weight ratio of the bishydantoin to the organophilic estersil in said mixture being about 1:1 to about 20:1, said organophilic estersil comprising a supercolloidal substrate coated with --OR' groups, the substrate having a surface of silica and having a specific surface area of from 25 to 900 square meters per gram, the coating of OR' groups being chemically bound to said silica and R being a hydrocarbon radical of from 3 to 6 carbon atoms, wherein the carbon atom attached to oxygen is also attached to hydrogen.

10. The lubricating composition of claim 9 wherein the bishydantoin is 1,1'-methy1enebis(5,5-dimethylhydantoin) and the organophilic estersil is an amorphous silica coated with about 340 butoxy groups per square millimicrons of surface.

11. A lubricating composition comprising a dispersion in a liquid polyorgano siloxane of a sufiicient amount to thicken the polyorgano siloxane to a grease consistency of l ,1 -methylenebis(5,5-dimethy1hydantoin) McCarthy et al. Apr. 11, 1961 McGrath et al. Apr. 11, 1961 

1. A LUBRICATING COMPOSITION COMPRISING A DIAPERSION IN A LUBRICATING OIL OF A SUFFICIENT AMOUNT TO THICKEN THE LUBRICATING OIL TO A GREASE CONSISTENCY OF A DISHYDANATOIN HAVING THE FOLLOWING STRUCTURAL FORMULA: 